High power electrical equipment, such as large electrical transformers, load tap changers, and circuit breakers, are typically immersed in oil, which is utilized to insulate and cool the power devices. Because the oil expands and contracts with temperature changes, such equipment is provided with a head space above the oil that is vented to the atmosphere to control pressure in, for example, a transformer tank. The pressure in the tank has to be maintained such that air bubbles, which can decrease the dielectric strength of the oil, are inhibited from developing in the oil.
When the heat in the tank increases, the oil in the tank expands, the pressure in the tank increases, and air in the reservoir is forced from the tank. When the tank begins to cool down, the oil in the tank contracts, the pressure in the tank decreases, and air is drawn into the tank to maintain the pressure in the tank.
A dehydrator breather is conventionally utilized to regulate airflow into and out of the tank. In some dehydrating breathers, a vent is provided between the vessel and the outside air. A valve is positioned between the vent and dehydrator breather container that controls the pressure in the tank by opening and closing, as necessary, to control air flow into and out of the tank.
Often, the dehydrator breather includes a desiccant material, such as a silica gel, to remove any moisture from the air before it is allowed into the tank. Water is a conductor, and thus, moisture entering the tank has the capability of destroying the electrical properties of the transformer.
Problems arise, however, when the desiccant escapes the desiccant container. For example, during shipment, the desiccant may break into fine pieces that escape the desiccant container. In addition, desiccant particles may pass through the valve with air that is exiting the dehydrator breather, and become trapped in the valve and/or trapped on top of the vent.
Further, moisture, which evaporates from the drying of the desiccant, often forms condensation on the walls of the dehydrator breather. When the condensation returns to a liquid state, it flows through the valve and out to the atmosphere via the holes in the vent. However, if the desiccant particles are trapped in the valve or clogging the vent, the moisture may become trapped in the vessel and the desiccant may be unable to dry out completely. As a result, the dehydrating breather will not be able to perform its drying functions.
Accordingly, it would be desirable to provide a dehydrator breather that does not allow desiccant particles, which may escape the desiccant container, from disturbing the operation of the dehydrator.